Composting, as is well known, is a controlled method of decomposition which transforms organic material (animal or vegetable) into a rich, brown earth-like substance called humus. While organic material can be composted either aerobically (with air) or anaerobically (without air), the present invention specifically relates to the aerobic composting of organic materials such as grass clippings, leaves and twigs. Of course, virtually any organic material, including newspaper, kitchen wastes, wood scraps, etc., can be composted but this discussion will focus primarily on aerobic composting of lawn and garden waste materials.
Composting is a self-decaying hot fermenting process, and certain conditions must exist in order for this process to be most efficient. For example, the microorganisms (bacteria and fungi, primarily) which decompose the organic material require balanced amounts of oxygen, water and nitrogen; and also work best within a certain temperature range and, it is believed, in the absence of sunlight. Since the present invention is directed to providing the ideal environment for the aerobic composting of lawn and garden waste, each of these conditions is discussed in greater detail below.
As noted above, composting microbes need oxygen to operate most efficiently. Ambient air is the normal source of oxygen for aerobic composting. The compost pile or heap must have enough ambient air to meet the oxygen requirements of the microbes; and enough ambient air to carry off waste gases generated as a by-product of the aerobic decomposition process.
Aerobic composting works best if the organic material is damp but not too wet. If there is too much water in the compost heap, the microbes will in effect be drowned and only slower anaerobic composting will take place. On the other hand, if the compost heap is too dry the microbes will not thrive. Thus, the oxygen and water requirements are somewhat at odds: there must be enough ambient air to meet the microbes' oxygen needs, but too much air can excessively dry the compost pile.
Nitrogen, another necessary ingredient of the aerobic composting "recipe," is provided through the organic material itself (e.g., grass or other nitrogen-rich material) or through the addition of a compost inoculant typically in the nature of a standard lawn and garden fertilizer. For grass composting, an inoculant may not be needed; whereas a 20-5-5 or 18-0-0 NPK fertilizer is preferable for the composting of leaves.
As to the temperature of the compost heap, a preferred temperature range is about 120.degree. F. to 160.degree. F. at the center of the pile. Aerobic composting is accelerated if the pile is insulated such that heat energy produced during the exothermic decaying process is, for the most part, contained within the compost heap.
Finally, the aerobic composting process seems to be accelerated in the dark; it is believed that some of the microbes are less effective when exposed to light.
Aerobic composting has been used for hundreds if not thousands of years. However, many of the composting methods and devices which have been tried over the years do not provide ideal aerobic composting conditions, as described above, or are unacceptable for other reasons. For example, simple compost piles having no wall structures to contain the composting material allow excessive heat loss from the pile; permit organic material (e.g., leaves) to blow away; subject the compost pile to excessive water in the event of a heavy rain, or insufficient water when the compost heap is exposed to drafts; potentially expose the pile to excessive sunlight; and are unsightly. While a simple uncontained compost pile is certainly cost effective and easy to mix, such a technique clearly has several disadvantages.
Presumably in an effort to make their compost piles less unsightly and to reduce water evaporation, some people have used pits or crude above-ground structures (e.g., rock walls) for containing their compost piles. One problem with this technique is that such pits or structures tend to excessively inhibit the flow of air to the compost pile. Further, the compost pile can still receive either too much or too little water. Also, it can be extremely difficult to mix the composting materials in a pit or crude structure (e.g., rock walls). Thus, even though compost pits or crude above-ground walled composters are cheap and easy to implement, generally they are not particularly effective.
Another common composting apparatus is constructed of chicken wire or the like. Typically a short section of the wire mesh is configured to form a cylindrical bin, with removable clips at the seam. Wire mesh composters are advantageous in that they are very inexpensive and they help prevent the composting materials from simply blowing away. However, the composting process can be inhibited because the organic material is either too wet (if exposed to a heavy rain) or too dry (if windy), and the material is exposed to sunlight which, it is believed, can reduce the effectiveness of some microbes. Also, particularly in high density urban or suburban areas, wire mesh compost bins can be objectionable from the standpoint of their appearance.
It's also difficult to adequately mix the contents of a wire mesh composter. The composter can, of course, be disassembled (typically by removing the clips at the seam) to allow mixing of the compost pile with a pitchfork or the like, but this is clearly a time consuming chore: the enclosure is disassembled; the pile mixed and turned over; and then the enclosure is reassembled. Alternatively, the contents of the composter can be mixed from the top, without disassembling the bin. The primary problem with the top mixing approach is that it is awkward. One has to lean over the top rim of the wire mesh enclosure and attempt to turn the pile with a shovel, pitchfork, or special tool. Since the wire mesh is very flimsy it is not possible to lean on or leverage off of the top rim of the enclosure.
To address some of the problems with unframed wire mesh composters of the type discussed above, various types of framed wire mesh composters have been constructed. For example, some framed wire mesh composters include doors for the removal of the fully composted material. Such structures still have several disadvantages, however. For example, they still fail to provide the ideal water/air balance, and as a class they do not accommodate easy mixing of the compost pile. Finally, because the composting material is quite visible there is still an aesthetics problem.
To address some of the problems associated with simple compost piles, compost pits and wire mesh bins, some individuals have used devices such as 55 gallon drums, with holes punched in the drum to permit the flow of air and water to the composting organic material. While such a device addresses many of the problems discussed above, it also does not allow for convenient mixing of the compost pile. The contents of the drum can be mixed to a degree by rolling the drum on the ground, or by rotating it in a stationary frame using a crank or the like. One problem with these mixing techniques is that very often the contents of the drum become so sticky that they simply clump into balls which skin over and resist composting. Thus it is felt that in order to get complete mixing and in order to achieve the most efficient composting conditions it is necessary to actually use a tool to turn over the composting material in the drum. A pitchfork or shovel could be used, through an open lid, but with great difficulty. To address this problem various "T" tools have been developed. The typical "T" tool has a handle, an elongated shaft and a pair of short tines at the lower end of the shaft. The "T" is formed at the bottom of the tool, by the tines and the shaft. Some "T" tools have pivoting tines, whereby when the working, or lower, end of the tool is inserted into the pile the tines fold inwardly toward the shaft; whereas when the tool is withdrawn the tines pivot outwardly, thereby forming a "T" shape at the bottom of the shaft, to pull at least some of the inner contents of the compost pile upwardly and outwardly, thereby turning the pile to a degree. As a class, such "T" tools aren't particularly effective, however. Organic composting materials are of such a consistency that they are not readily mixed simply by pulling up on the center of the pile with a small "T" shaped tool. In addition, pulling upwardly on such a "T" tool can be extremely awkward. Enclosed drums also do not take advantage of beneficial microbes and insects found in the soil. Finally, 55 gallon drum type composters are not particularly pleasing to the eye.
In an attempt to provide the ideal aerobic composting environment, as described above, and in an attempt to address some of the problems discussed above in connection with earlier aerobic composting techniques, some manufacturers have recently marketed slotted, box-like prefabricated composting bins, typically made of a molded plastic material, which can be assembled on site by the homeowner. One example of this type of bin is manufactured and sold by Barclay Mfg. Co. under the SoilSaver trademark. This type of compost bin includes slots or apertures which are intended to permit sufficient air flow to the compost pile while at the same time not permitting so much air flow that the compost pile becomes excessively dry. Such prefabricated compost bins also typically include some sort of lid to prevent excessive drying while at the same time shielding the compost pile from excessive rain and sunlight. Typically there is a lower door in the bin to permit removal of fully composted material.
While such prefabricated compost bins address many of the problems associated with earlier aerobic composting devices and techniques (e.g., simple compost piles, compost pits, etc.), such prefabricated bins still do not provide the ideal aerobic composting environment. For example, mixing the composting material is usually quite difficult, and such compost bins do not include means for metering the appropriate amount of rainwater to the pile. Mixing is typically accomplished by removing the lid and attempting to stir or turn the compost pile from the top using a shovel, pitchfork or "T" tool, as described above. As noted above, however, it is extremely difficult to effectively mix the entire contents of the pile by leaning over the upper edge of the bin and stirring the contents from the top. As to rainwater, typically the lids for such prefabricated bins include apertures, presumably to allow the flow of air and rainwater to the compost pile. But typically there are either not enough apertures or too many apertures to provide the proper balance of air and water to the compost pile. In addition, water/air apertures can admit excessive sunlight (thereby reducing, it is believed, the effectiveness of some of the microbes) and adversely impact the mechanical strength of the lid as well.
It should be noted that there are many other types of composters. The devices and techniques discussed above are representative of some of the more common types, but it should be understood that many other types of compost bins have been tried over the years.
The present invention is a method and apparatus for the aerobic composting of organic material, in particular lawn and garden waste such as grass clippings, leaves and twigs. The apparatus and method of the present invention provide the optimum aerobic composting environment and in particular meter in appropriate amounts of water, air and sunlight, and allow for easy mixing of the compost pile, so that the aerobic composting process can proceed at maximum efficiency.